Amorphization kinetics of germanium during ion implantation

We have experimentally studied by using transmission electron microscopy the kinetics of Ge amorphization during ion implantation at room temperature. We show that the critical damage energy density model, widely used in silicon under this or different names, can also be used in germanium to predict the existence, position, and extension of amorphous layers resulting from the implantation of ions for almost all mass/energy/dose combinations reported here and in literature. In germanium, the crystalline to amorphous phase transition occurs through the accumulation of damage (point defects and/or clusters), and this damage linearly increases with the dose (the damage is additive) until a certain threshold is reached above which the material turns amorphous. However, for light ions such as boron amorphization occurs, at room temperature, closer to the surface than expected. This demonstrates that the interstitials and vacancies generated by such implants are not stable at room temperature and that defect annihilation occurs within dilute cascades until stable complexes are formed, probably di-interstitials and divacancies. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3041653]